Rotor and rotor shaft for molten metal

ABSTRACT

A molten metal rotor receives and retains an end of a molten metal rotor shaft. The rotor shaft has one or more projections at the end received in the rotor. The rotor has an inner cavity, a top surface with an opening leading to the inner cavity, and at least one abutment. The opening includes one or more portions for allowing each projection to pass through the opening and into the inner cavity. The rotor and/or shaft are then rotated so at least one of the outwardly-extending projections is under the top surface of the rotor and is against an abutment. A molten metal pump, rotary degasser scrap melter or other device used in molten metal may utilize a rotor/shaft combination as disclosed herein.

CROSS REFERENCE TO RELATED APPLICATION

This application is a non-provisional of and claims priority to U.S.Provisional Application Ser. No. 62/020,332 entitled “Coupling and RotorShaft for Molten Metal Devices, filed on Jul. 2, 2014, the contents ofwhich are incorporated herein in its entirety for all purposes.

FIELD OF THE INVENTION

The inventions herein relate to devices used in molten metalenvironments and include (1) a rotor, and (2) a rotor shaft to beconnected to the rotor.

BACKGROUND OF THE INVENTION

As used herein, the term “molten metal” means any metal or combinationof metals in liquid form, such as aluminum, copper, iron, zinc andalloys thereof. The term “gas” means any gas or combination of gases,including argon, nitrogen, chlorine, fluorine, freon, and helium, thatare released into molten metal.

Known molten-metal pumps include a pump base (also called a housing orcasing), one or more inlets (an inlet being an opening in the housing toallow molten metal to enter a pump chamber), a pump chamber, which is anopen area formed within the housing, and a discharge, which is a channelor conduit of any structure or type communicating with the pump chamber(in an axial pump the chamber and discharge may be the same structure ordifferent areas of the same structure) leading from the pump chamber toan outlet, which is an opening formed in the exterior of the housingthrough which molten metal exits the casing. An impeller, also called arotor, is mounted in the pump chamber and is connected to a drivesystem. The drive system is typically an impeller shaft connected to oneend of a drive shaft, the other end of the drive shaft being connectedto a motor. Often, the impeller shaft is comprised of graphite, themotor shaft is comprised of steel, and the two are connected by acoupling. As the motor turns the drive shaft, the drive shaft turns theimpeller and the impeller pushes molten metal out of the pump chamber,through the discharge, out of the outlet and into the molten metal bath.Most molten metal pumps are gravity fed, wherein gravity forces moltenmetal through the inlet and into the pump chamber as the impeller pushesmolten metal out of the pump chamber.

This application incorporates by reference the portions of the followingpublications that are not inconsistent with this disclosure: U.S. Pat.No. 4,598,899, issued Jul. 8, 1986, to Paul V. Cooper, U.S. Pat. No.5,203,681, issued Apr. 20, 1993, to Paul V. Cooper, U.S. Pat. No.5,308,045, issued May 3, 1994, by Paul V. Cooper, U.S. Pat. No.5,662,725, issued Sep. 2, 1997, by Paul V. Cooper, U.S. Pat. No.5,678,807, issued Oct. 21, 1997, by Paul V. Cooper, U.S. Pat. No.6,027,685, issued Feb. 22, 2000, by Paul V. Cooper, U.S. Pat. No.6,123,523, issued Sep. 26, 2000, by Paul V. Cooper, U.S. Pat. No.6,303,074, issued Oct. 16, 2001, by Paul V. Cooper, U.S. Pat. No.6,689,310, issued Feb. 10, 2004, by Paul V. Cooper, U.S. Pat. No.6,723,276, issued Apr. 20, 2004, by Paul V. Cooper, U.S. Pat. No.7,402,276, issued Jul. 22, 2008, by Paul V. Cooper, U.S. Pat. No.7,507,367, issued Mar. 24, 2009, by Paul V. Cooper, U.S. Pat. No.7,906,068, issued Mar. 15, 2011, by Paul V. Cooper, U.S. Pat. No.8,075,837, issued Dec. 13, 2011, by Paul V. Cooper, U.S. Pat. No.8,110,141, issued Feb. 7, 2012, by Paul V. Cooper, U.S. Pat. No.8,178,037, issued May 15, 2012, by Paul V. Cooper, U.S. Pat. No.8,361,379, issued Jan. 29, 2013, by Paul V. Cooper, U.S. Pat. No.8,366,993, issued Feb. 5, 2013, by Paul V. Cooper, U.S. Pat. No.8,409,495, issued Apr. 2, 2013, by Paul V. Cooper, U.S. Pat. No.8,440,135, issued May 15, 2013, by Paul V. Cooper, U.S. Pat. No.8,444,911, issued May 21, 2013, by Paul V. Cooper, U.S. Pat. No.8,475,708, issued Jul. 2, 2013, by Paul V. Cooper, U.S. patentapplication Ser. No. 12/895,796, filed Sep. 30, 2010, by Paul V. Cooper,U.S. patent application Ser. No. 12/877,988, filed Sep. 8, 2010, by PaulV. Cooper, U.S. patent application Ser. No. 12/853,238, filed Aug. 9,2010, by Paul V. Cooper, U.S. patent application Ser. No. 12/880,027,filed Sep. 10, 2010, by Paul V. Cooper, U.S. patent application Ser. No.13/752,312, filed Jan. 28, 2013, by Paul V. Cooper, U.S. patentapplication Ser. No. 13/756,468, filed Jan. 31, 2013, by Paul V. Cooper,U.S. patent application Ser. No. 13/791,889, filed Mar. 8, 2013, by PaulV. Cooper, U.S. patent application Ser. No. 13/791,952, filed Mar. 9,2013, by Paul V. Cooper, U.S. patent application Ser. No. 13/841,594,filed Mar. 15, 2013, by Paul V. Cooper, and U.S. patent application Ser.No. 14/027,237, filed Sep. 15, 2013, by Paul V. Cooper.

Three basic types of pumps for pumping molten metal, such as moltenaluminum, are utilized: circulation pumps, transfer pumps andgas-release pumps. Circulation pumps are used to circulate the moltenmetal within a bath, thereby generally equalizing the temperature of themolten metal. Most often, circulation pumps are used in a reverbatoryfurnace having an external well. The well is usually an extension of thecharging well where scrap metal is charged (i.e., added).

Transfer pumps are generally used to transfer molten metal from the onestructure to another structure such as a ladle or another furnace.

Gas-release pumps, such as gas-injection pumps, circulate molten metalwhile introducing a gas into the molten metal. In the purification ofmolten metals, particularly aluminum, it is frequently desired to removedissolved gases such as hydrogen, or dissolved metals, such asmagnesium. As is known by those skilled in the art, the removing ofdissolved gas is known as “degassing” while the removal of magnesium isknown as “demagging.” Gas-release pumps may be used for either of thesepurposes or for any other application for which it is desirable tointroduce gas into molten metal.

Gas-release pumps generally include a gas-transfer conduit having afirst end that is connected to a gas source and a second end submergedin the molten metal bath. Gas is introduced into the first end and isreleased from the second end into the molten metal. The gas may bereleased downstream of the pump chamber into either the pump dischargeor a metal-transfer conduit extending from the discharge, or into astream of molten metal exiting either the discharge or themetal-transfer conduit. Alternatively, gas may be released into the pumpchamber or upstream of the pump chamber at a position where molten metalenters the pump chamber.

Molten metal pump casings and rotors often employ a bearing systemcomprising ceramic rings wherein there are one or more rings on therotor that align with rings in the pump chamber (such as rings at theinlet and outlet) when the rotor is placed in the pump chamber. Thepurpose of the bearing system is to reduce damage to the soft, graphitecomponents, particularly the rotor and pump base, during pump operation.

Numerous rotor shaft to motor shaft couplings are known. A problem withthe couplings, however, is that by applying driving force to the rotorshaft the rotor shaft tends to break at the location where the force isbeing applied. This is typically at the location where the coupling androtor shaft are in contact, and the broken end of the rotor shaft mustoften be chiseled out of an opening in the coupling in which it isretained.

Generally, a degasser (also called a rotary degasser) includes (1) animpeller shaft having a first end, a second end and a passage fortransferring gas, (2) an impeller, and (3) a drive source for rotatingthe impeller shaft and the impeller. The first end of the impeller shaftis connected to the drive source and to a gas source and the second endis connected to the connector of the impeller.

The materials forming the components that contact the molten metal bathshould remain relatively stable in the bath. Structural refractorymaterials, such as graphite or ceramics, that are resistant todisintegration by corrosive attack from the molten metal may be used. Asused herein “ceramics” or “ceramic” refers to any oxidized metal(including silicon) or carbon-based material, excluding graphite,capable of being used in the environment of a molten metal bath.“Graphite” means any type of graphite, whether or not chemicallytreated. Graphite is particularly suitable for being formed into pumpcomponents because it is (a) soft and relatively easy to machine, (b)not as brittle as ceramics and less prone to breakage, and (c) lessexpensive than ceramics.

Generally a scrap melter includes an impeller affixed to an end of adrive shaft, and a drive source attached to the other end of the driveshaft for rotating the shaft and the impeller. The movement of theimpeller draws molten metal and scrap metal downward into the moltenmetal bath in order to melt the scrap. A circulation pump may be used inconjunction with the scrap melter to circulate the molten metal in orderto maintain a relatively constant temperature within the molten metal.

Rotors are used in molten metal processing for a variety of purposes,such as in a pumping device to circulate molten metal, in a rotarydegasser to circulate molten metal and mix gas therewith, and in scrapmelters to help create a downward draw to pull scrap into the moltenmetal where the scrap is melted. The most common type of connectionbetween a rotor shaft and a rotor is to: (1) thread an end of the rotorshaft, (2) bore a threaded opening into the rotor, and (3) then screwthe threaded end of the rotor shaft into the threaded opening of therotor. Problems with this type of connection are that the threads canfail over time, thereby causing the rotor to move erratically and fail,and it is difficult to reverse the threaded end of the shaft to removethe rotor. Thus, if the rotor or rotor shaft fail, often both componentsmust be replaced.

SUMMARY OF THE INVENTION

The present invention alleviates these problems by providing a rotorthat includes a section for connecting to a rotor shaft. The connectingsection of the rotor has a cavity, an upper surface, and an opening inthe upper surface, the opening leading to the cavity. The opening has atleast one elongated section. The rotor shaft has an outer surface and asecond end with at least one projection extending therefrom, the secondend configured to fit through the opening in the upper surface of therotor (with the at least one projection passing through the at least oneelongated section). Once the second end of the rotor shaft is receivedin the cavity of the rotor, the rotor and/or rotor shaft are rotated sothe at least one projection is retained in a position under the topsurface and next to an abutment. As the rotor shaft turns the projectionpresses against the abutment to transmit driving force to the rotor.

In one preferred embodiment the rotor shaft has three or fourprojections, the opening in the upper surface has the same number ofelongated sections that respectively align with each of the projections.The second end of the rotor shaft passes through the opening and intothe cavity and is then rotated so each projection is positioned againsta respective abutment and under the upper surface of the rotor.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a pump for pumping molten metal, whichincludes a rotor and rotor shaft according to aspects of the invention.

FIG. 2 is a perspective view of a rotary degasser that may include arotor shaft and rotor according to aspects of the invention.

FIG. 3 is a perspective view of a scrap melter that may include a rotorshaft and rotor according to aspects of the invention.

FIG. 4 is a side view of a rotor shaft according to aspects of theinvention.

FIG. 5 is a view of the rotor shaft of FIG. 4.

FIG. 6 is a top view of a rotor according to aspects of the invention.

FIG. 7 is a side, cross-sectional view of the rotor of FIG. 6 takenalong lines A-A.

FIG. 8 is a top view of the rotor of FIG. 6 with the top surfaceremoved.

FIG. 9 is a side, perspective view of a rotor according to aspects ofthe invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to the drawing where the purpose is to illustrate anddescribe embodiments of the invention, and not to limit same, FIG. 1shows a molten metal pump 20 that includes a rotor shaft 44 and rotor100 in accordance with aspects of the present invention. During use,pump 20 is usually positioned in a molten metal bath B in a pump well,which may be part of the open well of a reverbatory furnace.

FIG. 2 shows an example of a rotary degasser that could potentially usea rotor shaft/rotor connection in accordance with aspects of theinvention and FIG. 3 shows an example of a scrap melter that couldpotentially use a rotor shaft/rotor connection in accordance withaspects of the invention. Rotor shaft 44′ of rotary degasser 200 is inall respects the same as rotor shaft 44 described below with respect tothe way in which it couples to rotor 300.

The components of pump 20, including rotor 100, that are exposed to themolten metal are preferably formed of structural refractory materials,which are resistant to degradation in the molten metal. Carbonaceousrefractory materials, such as carbon of a dense or structural type,including graphite, graphitized carbon, clay-bonded graphite,carbon-bonded graphite, or the like have all been found to be mostsuitable because of cost and ease of machining Such components may bemade by mixing ground graphite with a fine clay binder, forming thenon-coated component and baking, and may be glazed or unglazed. Inaddition, components made of carbonaceous refractory materials may betreated with one or more chemicals to make the components more resistantto oxidation. Oxidation and erosion treatments for graphite parts arepracticed commercially, and graphite so treated can be obtained fromsources known to those skilled in the art.

Pump 20 can be any structure or device for pumping or otherwiseconveying molten metal, such as the pump disclosed in U.S. Pat. No.5,203,681 to Cooper, or an axial pump having an axial, rather thantangential, discharge. One preferred pump 20 has a pump base 24 forbeing submersed in a molten metal bath. In this embodiment, pump base 24preferably includes a generally nonvolute pump chamber 26, such as acylindrical pump chamber or what has been called a “cut” volute,although pump base 24 may have any shape pump chamber suitable of beingused, including a volute-shaped chamber. Chamber 26 may have only oneopening, either in its top or bottom, since only one opening is requiredto introduce molten metal into pump chamber 26, although chamber 26 mayhave an opening in both its top and bottom. Generally, pump chamber 24has two coaxial openings of the same diameter and usually one is blockedby a flow blocking plate mounted on the bottom of, or formed as part of,rotor 100. Base 24 further includes a tangential discharge 30 (althoughanother type of discharge, such as an axial discharge may be used) influid communication with chamber 26.

The invention is not limited to any particular type or configuration ofbase, or of even having a base. A pump used with the invention could beof any size, design or configuration suitable for utilizing a rotorshaft and rotor according to the invention.

In the preferred embodiment, post clamps 35 secure posts 34 tosuperstructure 36. In the embodiment shown, one or more support posts 34connect base 24 to a superstructure 36 of pump 20 thus supportingsuperstructure 36, although any structure or structures capable ofsupporting superstructure 36 may be used. Additionally, pump 20 could beconstructed so there is no physical connection between the base and thesuperstructure, wherein the superstructure is independently supported.The motor, drive shaft and rotor could be suspended without asuperstructure, wherein they are supported, directly or indirectly, to astructure independent of a pump base.

A motor 40, which can be any structure, system or device suitable forpowering pump 20, but is preferably an electric or pneumatic motor, asshown is positioned on superstructure 36 and is connected to an end of adrive shaft 42. Drive shaft 42 can be any structure suitable forrotating a rotor (also called an impeller), and preferably comprises amotor shaft (not shown) coupled to rotor shaft 44. The motor shaft has afirst end and a second end, wherein the first end of the motor shaftconnects to motor 40 and the second end of the motor shaft connects to acoupling.

Rotor shaft 44 is shown in FIGS. 1, 4 and 5 and has a first end 44A thatconnects to the coupling and a second end 44B that connects to rotor100, best seen in FIGS. 6-9. End 44A can connect to a coupling in anysuitable manner.

End 44B of rotor shaft 44 has at least one outwardly-extendingprojection 50, and as shown has four outwardly-extending projections 50equally radially spaced about the outer surface 52 (which as shown iscylindrical or annular) of rotor shaft 44, although any suitable numberof projections may be used. Each projection 50 can be of any suitablesize or shape, and at any suitable location on end 44B of rotor shaft44. In one embodiment each projection 50 is generally rectangular,between ⅜″ and 1½″ wide, between ¾″ and 3″ in length (as measured alongthe longitudinal axis of rotor shaft 44) and extends outward from rotorshaft 44 by ¼″ to 2½″. Each projection 50 can be integrally formed withor attached to rotor shaft 44. For example, a slot (not shown) may beformed in rotor shaft 44 and a projection 50 could be cemented orotherwise affixed into the slot. Each slot (if used) is preferably about1/32″ to ¼″ wider and longer than the width and length of the projection50 that fits therein, and each slot and could be between 3/16″ to 1″deep in rotor shaft 44. Second end 44B also may include a chamferedportion 54 that assists in positioning the second end 44B into aconnective portion 110 in rotor 100. If rotor shaft 44 is used in arotary degasser, it would preferably have an internal passage (notshown) for the transfer of gas from first end 44A to second end 44B.

One preferred rotor 100, shown in FIGS. 6-9, could be of any shape orsize suitable to be used in a molten metal pump, a rotary degasser orscrap melter, respectively, with the present invention being directed tothe connection between the rotor shaft and the rotor and the respectivestructures of the rotor shaft end 44B and rotor connective portion.Rotor 100 is preferably circular in plain view (although it can be ofany suitable shape for its intended use) and includes a displacementstructure 102, an inlet structure 104, a top surface 106, a bottomsurface 108, and a connective portion 110. Rotor 100 could be comprisedof a single material, such as graphite or ceramic, or could be comprisedof different materials. For example, inlet structure 104 may becomprised of ceramic and the displacement structure 102 may be comprisedof graphite, or vice versa. Any part or all of rotor 100 may alsoinclude a protective ceramic coating.

Connective portion 110 connects to end 44B of rotor shaft 44. Connectiveportion 110 preferably includes (1) an upper surface 300, (2) an opening302 in upper surface 300, the opening 302 as shown in this embodimentbeing generally circular and having at least one elongated section 304,and as shown, four elongated sections 304, (3) a cavity 306 beneathupper surface 300 and in communication with each elongated portion 304,and (4) at least one abutment 308 within each cavity 306.

The at least one abutment 308 is adjacent to the at least one elongatedsection 304 and on the rotational downstream side of elongated section304. In this manner, when shaft 44 is rotated during operation,rotational driving force is transmitted to rotor 100 by the at least oneprojection 50 pushing against and transmitting force to the at least oneabutment 308. Further, the rotation of shaft 44 during operation wouldnot move a projection 50 back into alignment with a correspondingelongated portion 304, which could lead to the rotor 100 and shaftsecond end 44B separating.

To connect the rotor shaft 44 to rotor 100, end 44B of rotor shaft 44 ismoved through opening 302. The rotor shaft 44 and/or rotor 100 arerotated until at least one projection 50 is under upper surface 300 andpressed against an abutment 308. In this manner the rotor shaft 44 isconnected to rotor 100 and can provide rotational driving force thereto.

Having thus described different embodiments of the invention, othervariations and embodiments that do not depart from the spirit of theinvention will become apparent to those skilled in the art. The scope ofthe present invention is thus not limited to any particular embodiment,but is instead set forth in the appended claims and the legalequivalents thereof. Unless expressly stated in the written descriptionor claims, the steps of any method recited in the claims may beperformed in any order capable of yielding the desired product.

What is claimed is:
 1. A rotor shaft having a first end that is receivedin a coupling and a second end connected to a rotor having a rotorcavity, the second end having at least one outwardly-extendingprojection that is received and retained in the rotor cavity in order toconnect the second end to the rotor; wherein the rotor shaft has anannular outer surface and the at least one outwardly-extendingprojection extends outward at least ½″ from the annular outer surface;the rotor further having a top surface with a rotor opening throughwhich the second end of the rotor shaft passes into the rotor cavity,the rotor opening having at least one elongated section through whichthe at least one outwardly-extending projection passes, wherein therotor cavity has a diameter and the rotor opening has a width, the widthof the rotor opening being less than the diameter of the rotor cavity,and the rotor cavity including at least one abutment against which theat least one outwardly-extending projection is positioned when thesecond end of the rotor shaft is in the rotor cavity and the rotor androtor shaft are rotated relative one another.
 2. The rotor shaft ofclaim 1 that is comprised of one or more of the group consisting of:graphite and ceramic.
 3. The rotor shaft of claim 1 wherein the secondend has a plurality of outwardly-extending projections.
 4. The rotorshaft of claim 3, wherein the plurality of outwardly-extendingprojections are spaced equidistant from one another.
 5. The rotor shaftof claim 3 that has three outwardly-extending projections.
 6. The rotorshaft of claim 5, wherein the rotor cavity has three abutments.
 7. Therotor shaft of claim 5, wherein rotor opening includes three elongatedsections.
 8. The rotor shaft of claim 3, wherein each of the pluralityof outwardly-extending projections extends outward at least ½″ from theannular outer surface.
 9. The rotor shaft of claim 3, wherein each ofthe plurality of outwardly-extending projections comprises ceramic. 10.The rotor shaft of claim 3 that further includes the rotor connected tothe second end of the rotor shaft, the rotor having the rotor cavity inwhich the second end of the rotor shaft is positioned, and a top surfacewith a rotor opening, the rotor opening leading to the rotor cavity andhaving a plurality of elongated sections configured so that a single oneof the plurality of outwardly-extending projections passes through asingle one of the plurality of elongated sections, and the rotor cavityincludes a plurality of abutments, and a single one of the plurality ofoutwardly-extending projections is positioned against a single one ofthe plurality of abutments when the rotor and rotor shaft are rotatedrelative one another.
 11. The rotor shaft of claim 3, wherein the rotoropening includes a plurality of elongated sections.
 12. The rotor shaftof claim 1, wherein the at least one outwardly-extending projectioncomprises ceramic.
 13. The rotor shaft of claim 1 that further includesthe rotor connected to the second end of the rotor shaft, the rotorcavity having the second end of the rotor shaft positioned therein, anda top surface with a rotor opening through which the second end of therotor shaft passes into the rotor cavity, the rotor opening having atleast one elongated section through which the at least oneoutwardly-extending projection passes, and the rotor cavity including atleast one abutment against which the at least one outwardly-extendingprojection is positioned when the rotor and rotor shaft are rotatedrelative one another.
 14. The rotor shaft of claim 13, wherein the rotorcavity has a diameter and the rotor opening has a width, the width ofthe rotor opening being less than the diameter of the rotor cavity. 15.The rotor shaft of claim 13, wherein the rotor opening has a first widththat does not include the at least one elongated section and a secondwidth that includes the at least one elongated section, the first widthbeing less than the second width.
 16. The rotor shaft of claim 15,wherein the rotor cavity has a diameter and the first width and secondwidth are each less than the diameter.
 17. The rotor shaft of claim 13,wherein the top surface of the rotor comprises ceramic.
 18. A moltenmetal pump comprising: (a) a motor; (b) a motor shaft extending from themotor and having an end; (c) a coupling that couples to the end of themotor shaft; (d) a rotor shaft having a first end that is received inthe coupling and a second end for connecting to a rotor, the second endhaving at least one outwardly-extending projection that is received andretained in a rotor cavity in order to connect the second end to therotor; wherein the rotor shaft has an annular outer surface and the atleast one outwardly-extending projection extends outward at least ½″from the annular outer surface; and (e) wherein the rotor has a topsurface with a rotor opening through which the second end of the rotorshaft passes into the rotor cavity, the rotor opening having at leastone elongated section through which the at least one outwardly-extendingprojection passes, and the rotor opening has a first width that does notinclude the at least one elongated section and a second width thatincludes the at least one elongated section, the first width being lessthan the second width, and the rotor cavity including at least oneabutment against which the at least one outwardly-extending projectionis positioned when the second end of the rotor shaft is in the rotorcavity and the rotor and rotor shaft are rotated relative one another.19. The molten metal pump of claim 18, wherein the rotor openingincludes a plurality of elongated sections.
 20. The molten metal pump ofclaim 19, wherein the rotor opening includes three elongated sections.21. The molten metal pump of claim 18, wherein the rotor cavity has adiameter and the rotor opening has a width, the width of the rotoropening being less than the diameter of the rotor cavity.
 22. The moltenmetal pump of claim 18, wherein the rotor cavity has a diameter and thefirst width and second width are each less than the diameter.
 23. Themolten metal pump of claim 18, wherein the top surface of the rotorcomprises ceramic.
 24. The molten metal pump of claim 18, wherein therotor shaft is comprised of one or more of ceramic and graphite.
 25. Arotary degasser comprising: (a) a motor; (b) a motor shaft extendingfrom the motor and having an end; (c) a coupling that couples to the endof the motor shaft; (d) a rotor shaft having a first end that isreceived in the coupling and a second end for connecting to a rotor, thesecond end having at least one outwardly-extending projection that isreceived and retained in a rotor cavity in order to connect the secondend to the rotor; wherein the rotor shaft has an annular outer surfaceand the at least one outwardly-extending projection extends outward atleast ½″ from the annular outer surface; and (e) wherein the rotor has atop surface with a rotor opening through which the second end of therotor shaft passes into the rotor opening cavity, the rotor openinghaving at least one elongated section through which the at least oneoutwardly-extending projection passes, and the rotor cavity including atleast one abutment against which the at least one outwardly-extendingprojection is positioned when the second end of the rotor shaft is inthe rotor cavity and the rotor and the rotor shaft are rotated relativeone another, wherein the rotor cavity has a diameter and the rotoropening has a width, the width of the rotor opening being less than thediameter of the rotor cavity.
 26. The rotary degasser of claim 25,wherein the rotor shaft is comprised of one or more of ceramic andgraphite.
 27. The rotary degasser of claim 25, wherein the rotor openingincludes a plurality of elongated sections.
 28. The rotary degasser ofclaim 27, wherein the rotor opening includes three elongated sections.29. The rotary degasser of claim 25, wherein the rotor opening has afirst width that does not include the at least one elongated section anda second width that includes the at least one elongated section, thefirst width being less than the second width.
 30. The rotary degasser ofclaim 29, wherein the cavity has a diameter and the first width andsecond width are each less than the diameter.
 31. The rotary degasser ofclaim 25, wherein the top surface of the rotor comprises ceramic.
 32. Ascrap melter comprising: (a) a motor; (b) a motor shaft extending fromthe motor and having an end; (c) a coupling that couples to the end ofthe motor shaft; (d) a rotor shaft having a first end that is receivedin the coupling and a second end for connecting to a rotor, the secondend having at least one outwardly-extending projection that is receivedand retained in a rotor cavity in order to connect the second end to therotor; wherein the rotor shaft has an annular outer surface and the atleast one outwardly-extending projection extends outward at least ½″from the annular outer surface; and (e) wherein the rotor has a topsurface with a rotor opening through which the second end of the rotorshaft passes into the rotor cavity, wherein the rotor cavity has adiameter and the rotor opening has a width, the width of the rotoropening being less than the diameter of the rotor cavity, the rotoropening having at least one elongated section through which the at leastone outwardly-extending projection passes, and the rotor cavityincluding at least one abutment against which the at least oneoutwardly-extending projection is positioned when the second end of therotor shaft is in the rotor cavity and the rotor and the rotor shaft arerotated relative one another.
 33. The scrap melter of claim 32, whereinthe rotor shaft is comprised of one or more of ceramic and graphite. 34.The scrap melter of claim 32, wherein the rotor opening includes aplurality of elongated sections.
 35. The scrap melter of claim 34,wherein the rotor includes three elongated sections.
 36. The scrapmelter of claim 32, wherein the rotor opening has a first width thatdoes not include the at least one elongated section and a second widththat includes the at least one elongated section, the first width beingless than the second width.
 37. The scrap melter of claim 36, whereinthe rotor cavity has a diameter and the first width and second width areeach less than the diameter.
 38. The scrap melter of claim 32, whereinthe top surface of the rotor comprises ceramic.